From manufacturing to power generation and more, heat transfer fluids are necessary to a wide variety of processes as a means of cooling and/or heating by the transfer of energy using both thermal conduction with the fluid and movement of the fluid between a heat source and a heat sink. Typically, one or more heat exchangers within a heat exchange system are used for the transfer of heat to and from the heat transfer fluid. The efficiency and capacity of a heat exchange system can be improved upon by e.g., increasing the velocity of the heat transfer fluid within the system and/or increasing the surface area available for heat transfer. Unfortunately, such steps generally come at increased operating and/or equipment expense and may be impractical as a retrofit of an existing heat exchange system.
The identity of the component(s) used as the heat transfer fluid will also affect heat exchange. Typically, a heat transfer fluid having increased thermal conductivity and/or increased heat capacity can improve the efficiency and capacity of a heat exchange system. However, it also preferable that the heat transfer fluid remain stable at high temperatures, exhibit Newtonian flow, have a low volatility, and demonstrate compatibility with the materials used in the construction of the system. Unfortunately, heat transfer fluids that are currently in widespread use (e.g., water, ethylene glycol, engine oil) do not necessarily possess all of these desirable properties.
The thermal conductivities of solids are typically much higher than conventional heat transfer fluids such as water or oil. For example, the thermal conductivity of copper at room temperature is approximately 700 times higher than water. Accordingly, the dispersion of certain solids into a conventional heat transfer fluid has been investigated. Carbon nanoparticles dispersed into conventional heat transfer fluids such as ethylene glycol or mixtures of ethylene glycol and water are indicated in U.S. Pat. No. 6,695,974. The efficiency of the these mixtures as heat transfer fluids is, however, still limited by the relatively low thermal conductivity and/or heat capacity of water and ethylene glycol.
Accordingly, a need still exists for heat transfer fluids having improved efficiencies and capacities. More specifically, a need still exists for heat transfer fluids having relatively larger heat capacities and higher thermal conductivities that remain stable at higher temperatures, exhibit low volatility, transport with Newtonian flow, and are compatible with the materials used in modern heat exchange systems.